Impacts of Momentum Roughness Length on Hurricane Development
The momentum roughness length (z0) significantly impacts wind predictions in weather and climate models. Nevertheless, the impacts of z0 parameterizations in different wind regimes and various model configurations on the hurricane size, intensity, and track simulations have not been thoroughly established.
To bridge this knowledge gap, a comprehensive analysis of 310 simulations of 10 real hurricanes using the Weather Research and Forecasting (WRF) model is conducted in comparison with observations. Our results show that the default z0 parameterizations in WRF perform well for weak (category 1-2) hurricanes; however, they underestimate the intensities of strong (category 3-5) hurricanes. This finding is independent of model resolution or boundary layer schemes. The default values of z0 in WRF agree with the observational estimates from dropsonde data in weak hurricanes while they are much larger than observations in strong hurricanes regime. Decreasing z0 close to the values of observational estimates and theoretical hurricane intensity models in high wind regimes (≳ 45 m s-1) led to significant improvements in the intensity forecasts of strong hurricanes. A momentum budget analysis dynamically explained why the reduction of z0 (decreased surface turbulent s tresses) leads to stronger simulated storms.
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